Tire breaker strip with folded plies

Abstract

A radial tire with improved uniformity of transverse stiffness of its breaker. In the preferred embodiment, two superimposed folded-edge steel cord plies are placed over and under one or more layers of cords formed of a material having a zero or negative temperature coefficient of expansion. This material is preferably nylon.

Having now described my invention what I claim is: 
     
       1. A vehicle tire of the radial carcass type and having a breaker structure comprising a first radially inwardly steel cord ply having a bias angle between 16° and 25° and having one edge thereof folded radially outwardly and axially inwardly of the tire to form a double thickness layer extending transversely of the breaker by an amount less than half the overall width of the breaker, a second steel cord ply disposed radially outwardly of said first steel cord ply and the folded edge thereof, said second steel cord ply having one edge thereof on the transversely opposite side of the breaker from the folded edge of said first steel cord ply, folded radially inwardly and axially inwardly of the tire to form a double-thickness layer extending transversely of the breaker by an amount less than half the overall width of the breaker, the axially inward edges of the folded edges being spaced apart transversely of the breaker, and at least one further cord layer located radially between the first and second steel cord plies and axially between said spaced-apart axially inward edges of the folded edges but without overlapping said folded edges, the cords of said at least one further cord layer having a bias angle of not more than 10° and being of a material which has a zero or negative temperature coefficient of expansion to provide a substantially uniform elastic modulus across the width of the breaker. 
     
     
       2. A vehicle tire of the radial carcass type and having a breaker structure comprising a first radially inwardly steel cord ply having a bias angle of about 22° and having one edge thereof folded radially outwardly and axially inwardly of the tire to form a double thickness layer extending transversely of the breaker by about one-fifth the overall width of the breaker, a second steel cord ply disposed radially outwardly of said first steel cord ply and the folded edge thereof, said second steel cord ply having one edge thereof on the transversely opposite side of the breaker from the folded edge of said first steel cord ply, folded radially inwardly and axially inwardly of the tire to form a double-thickness layer extending transversely of the breaker by about one-fifth the overall width of the breaker, the axially inward edges of the folded edges being spaced apart transversely of the breaker, and at least one further cord layer having an axial width of about three-fifths the overall width of the breaker and located radially between the first and second steel cord plies and axially between said spaced-apart axially inward folded edges, having a bias angle of not more than 10° and the cords of said at least one further cord layer being of a material which has a zero or negative temperature coefficient of expansion. 
     
     
       3. A tire according to claim 2 wherein said range of angles is limited to not more than five degrees on either side of said plane. 
     
     
       4. A tire according to claim 1, wherein said number of further cord layers is from one upwards and said number together with the elastic modulus of the cords thereof and of the steel cords forms a breaker structure with reduced transverse variations in the elastic modulus of the breaker as a whole to a value below a predetermined limit. 
     
     
       5. A tire according to claim 4 wherein said number and modulus are chosen to give the complete breaker structure a substantially uniform transverse elastic modulus. 
     
     
       6. A tire according to claim 1, wherein there are at least two of said further layers and the cords in adjacent layers are oppositely inclined with respect to the mid-circumferential plane of the tire. 
     
     
       7. A tire according to claim 6 wherein the cords in adjacent ones of said at least two further layers are equally and mutually oppositely inclined with respect to said mid-circumferential plane. 
     
     
       8. A tire according to claim 1 wherein the cords of each said further layer are composed of nylon. 
     
     
       9. A vehicle tire of the radial carcass type and having a breaker structure comprising a first radially inwardly steel cord ply having a bias angle between 16° and 25° and having one edge thereof folded radially outwardly and axially inwardly of the tire to form a double thickness layer extending transversely of the breaker by about one-fourth the overall width of the breaker, a second steel cord ply disposed radially outwardly of said first steel cord ply and the folded edge thereof, said second steel cord ply having a bias angle between 16° and 25° and having one edge thereof on the transversely opposite side of the breaker from the folded edge of said first steel cord ply, folded radially inwardly and axially inwardly of the tire to form a double-thickness layer extending transversely of the breaker by about one-fourth the overall width of the breaker, the axially inward edges of the folded edges being spaced apart transversely of the breaker, and at least one further cord layer having an axial width of about one-half the overall width of the breaker and located radially between the first and second steel cord plies and axially between said spaced-apart axially inward edges of the folded edges, the cords of said at least one further cord layer having a bias angle of not more than 10° and being of a material which has a zero or negative temperature coefficient of expansion.